Process for the preparation of an alpha-chloro-pyridine



Patented Apr. 19, 1932 UNITED STATES PATENT OFFICE KARL VIEWEG, OF FRANKFORT-ON-THE-MAIN, GERMANY, ASSIGNOR TO DEUTSCHE GOLD 8c SILBER SCHEIDEANSTALT VORMALS BOESSLER, OF FRANKFORT-ON-THE MAIN, GERMANY, A CORPORATION PROCESS FOR THE PREPARATION OF AN' a-CHLOR-O-PYRIDINE No Drawing. Application filed November 29, 1927,Seria1 No. 236,586, and in Germany December 3, 1926.

It is already known that an N-alkyl-a-pyridone can be converted into d-chloro-pyridine by treatment with phosphorous pentachloride.

I have now found that it is possible to convert N-alkyl-u-pyridones into a-chloro-pyridine by treating the pyridones with the considerably cheaper compound, phosgene. This reaction takes place at about the same temperature as that required when phosphorous pentachloride is used as the chlorinating agent. The preparation of a-chloro- Eyridines by my invention is not only cheaper ut is accomplished with much less trouble than by other methods, since the by-products, carbon dioxide and alkyl chloride, may be led ofl as gases during the reaction. Excellent yields of final product are obtained when using my process.

The following examples will serve to illustrate my invention.

Ezvamp les ing it with a little caustic soda solution and then steam distilled. There were obtained about 39 grs. of a-chloro-pyridine, which corresponds to a yield of about 93-94%.

I believe the reaction which occurred in this example is substantially as follows:

+COCl2- +COi+CHsCl 0 Cl N N ml.

(2) grs. of N-methyl-B'-nitro-ayridone were put into a flask fitted with a re ux condenser and chlorinated by slowly introducing phosgene at temperatures of about 130 to 160. finished; the weight of mass is about 51 grs.

N-alkyl-a-pyridone by means of heating'with phosgene. V

Signed at Frankfort-on-the-Main, Germany, this 7th day of November, A. D. 1927. KARL VIEWEG.

After two hours the chlorination is 

